Becoming an actor in Sydney, Australia?

I'm 19 and have wanted to become an actor for as long as I remember. I have a lot of modeling experience, am comfortable in front of the camera and have taken acting classes in the form of NIDA short courses. Most of the big agencies here won't take you on unless you have experience/a show reel but how do I get that/auditions without them? I'm continuing to study the art but I think at this point I need some practical experience even if it is only small roles. My main aim is TV/Screen but if I need to do theater work to gain experience , I am willing. I just don't know the next step. Who do I contact? What legitimate agencies would help me build my experience? Or am I better off going alone? How does someone become an actor in Sydney, Australia?